https://www.mongodb.com/docs/manual/core/aggregation-pipeline-optimization/

https://www.mongodb.com/docs/manual/reference/operator/aggregation/

$$this is map `as` default var ref

db.collection.update({},
[
  {
    $set: {
      "images": {
        $map: {
          input: "$images",
          in: {
            $replaceOne: {
              input: "$$this",
              find: "image.xxxx.com",
              replacement: "image.xxxx.cn"
            }
          }
        }
      }
    }
  }
],
{
  multi: true
})

https://mongoplayground.net

db.collection.update({},
[
  {
    $set: {
      "image": {
        $replaceOne: {
          input: "$image",
          find: "resource.intbird.cn",
          replacement: "image.intbird.cn"
        }
      }
    }
  }
],
{
  multi: true
})

$unwind

https://www.mongodb.com/docs/manual/reference/operator/aggregation/unwind/

$push

https://www.mongodb.com/docs/manual/reference/operator/aggregation/group/

const test = [
  {
    '$match': {
      'id': 1
    }
  }, {
    '$unwind': '$users'
  }, {
    '$match': {
      'users.type': 1
    }
  }, {
    '$group': {
      '_id': '$_id', 
      'users': {
        '$push': '$users.type'
      }
    }
  }
];